Aseptic packages refer to sealed containers containing a substantially uniform predetermined amount of a product made in accordance with commercial aseptic packaging standards. Commercial aseptic packaging involves introducing a sterile product into a sterile container and then hermetically sealing the container in an environment substantially free of microorganisms capable of growing in a shelf stable product at temperatures at which the finished product is likely to be stored during distribution and storage prior to consumption. Hermetically sealed containers minimize the transmission of any gas or fluid through the container package so that there is substantially no biological transmission. Preferably, the package is also substantially free of air which, if present in significant amounts, could promote undesired microbial growth or, even in the absence of microbial growth, adversely affect the taste or color of a product. Typical products are fluent materials, specifically, a fluid drink such as pasturized milk, fruit juices, and the like.
The sterile containers commonly comprise a laminated web packaging material preferably having at least one layer of current carrying material such as aluminum foil, a first exterior layer of thermoplastic material to become the package interior in contact with the product, and a second exterior layer of material for contact with the environment. The laminated material, also referred to herein as "polyfoil web", is typically strong enough to stand upright in a somewhat rigid finished configuration to contain the product for shipping and storage. and commonly includes a conventional paperboard structural layer. Product labeling may be printed on the paperboard layer or the outer thermoplastic layer. Regarding the invention described below, the most preferred polyfoil web to use comprises a laminate of, in order, a layer of low density polyethylene, paper stock, Surlyn.RTM., aluminum foil, Surlyn.RTM., and linear low density polyethylene. The low density polyethylene layer could also be a high density polyethylene, and the linear low density polyethylene layer could also be a low density polyethylene.
The thermoplastic material forming the package interior must be capable of being sealed together to form hermetic seals. Typically, opposing thermoplastic layers are heated to a melting temperature so that they will fuse together. The thermoplastic and metallic foil layers act in concert to provide the hermetic barrier for the aseptic package. The metallic foil layer provides a light and oxygen barrier. The outer layer is commonly a thermoplastic material that can be heated so that the excess material formed during final forming or bricking of the packages can be flattened or tacked against the package sidewalls to form an aesthetically pleasing package. Such polyfoil laminates may include spaced access means to enable the user to readily extract the product from the finished package.
Several methods and machines for forming aseptic and non aseptic packages or cartons from paper stock and laminated web materials are known. These methods and machines generally fall into two categories. blank fed and web fed.
In blank fed machines, the supply of web first is separately formed into cut and scored blanks. The blanks are then fed into the forming section of the machine one at a time and erected into containers. One commercial blank fed aseptic machine is Combiblok, Model No. CF 606A.
In web fed machines, the web is taken directly off the roll of flat web stock, scored (unless prescored), and fed into the machine. The machine then folds the web about a forming means, for example a square or tubular forming mandrel, a circular wire guide means, or a series of guide rollers and stationary guide means to form a longitudinally extending column. The longitudinal edges are then sealed together to form a tube. The tube is filled with a product, and then clamped, sealed, and severed transversely to form packages which can be formed into a brick shape.
The web advance may be continuous, to gradually manipulate the web into sealed packages, or intermittent, to perform each forming and sealing operation either while the web is stationary or while the web is moving between stations. The sealing steps typically involve thermally sealing thermoplastic materials together to form an hermetic seal. Thermal sealing is brought about by using, for example, radiant heat and means for pressing the heated materials together, opposing heated contacting members such as nichrome wires, or induction heating coils (for webs having a conductive layer integrated therein or applied thereon). One commercial automatic continuous feed aseptic machine is Tetra-Pak Model AB 9. Other known aseptic machines include International Paper Co.'s web fed aseptic package machine, Model SA.
The primary problem with the aforementioned forming, filling, and sealing machines is that they are limited in the machine speed and web control required to continuously or intermittently make aseptic packages at a rate of speed higher than presently obtainable in an economically efficient manner. The present invention relates to an improvement in web fed type machines, and is designed to have a production rate substantially higher than that of presently known machines.
Intermittent and continuous advance web fed machines are limited by the rate at which the web can be advanced and formed into a longitudinally advancing tube and then sealed and severed transversely into packages.
It is therefore an object of this invention to provide an improved method and apparatus for forming a flat web of polyfoil material into a longitudinally advancing tube at high rates of speed. It is also an object to provide such a method and apparatus for tube forming under aseptic conditions.
It is another object to manipulate the web into a substantially triangular configuration in preparation for forming a tube in order to facilitate package forming. It is also an object to provide a forming roller at the base of the triangular configuration to reduce the number of fold lines present in the final rectangular package and aid in aligning the edges to be sealed together.